This relates to splittable catheters used in connection with aiding insertion of long-line catheters into a human body. The technique of the preferred arrangement for inserting a long-line catheter includes making the venipuncture with a hollow needle that carries coaxially thereover a splittable placement catheter. Once the vein has been penetrated and blood is visible in the flashback chamber, the needle and flashback chamber are removed leaving the placement catheter through the site of the puncture and in the vein. A long-line catheter or guidewire is threaded through the placed catheter and thereafter the catheter is removed from the vein leaving the guidewire or the long-line catheter in place. The removed placement catheter is designed to split longitudinally so that same can be taken away from the guidewire or the long-line catheter without difficulty.
A variety of approaches have been disclosed for facilitating the longitudinal split of the placement catheter. For example, the Boarini et al U.S. Pat. No. 4,411,654 shows various catheter cross sectional configurations including rupture lines produced by mechanically scoring the catheter tube or preferably by placing same in the tube during extrusion. Fabrication of each cross sectional configuration is very difficult since polymer materials have a memory and therefore tend to knit (extrusion) or split (scoring).
The rupture lines are provided to produce a uniform weakness in the catheter tube assisting smooth longitudinal tearing of the tube during removal. It has also been suggested to provide rupture lines by use of oriented polymer material formed by extrusion. In addition to the scoring, the rupture line of weakness could be merely an opening or lumen extending through the length of the wall of the tubing. The Buhler et al U.S. Pat. No. 4,402,685 discloses an incompatible polymer simultaneously extruded with a base polymer to form two semi-circular walls which are joined to two strips of the simultaneously extruded modified polymer. The strips are located 180.degree. apart such that the catheter tube is readily divided by tearing the juncture between the base polymer and the modified polymer.
German Patent No. 2,104,226 discloses a short catheter polymeric tube having longitudinal tear lines or fracture points produced by molding or machining a preformed polymeric tube with a uniform wall thickness such that the tearing or ripping is a function of the residual wall thickness at the tear line. The Osborne U.S. Pat. No. 4,306,562 discloses a splittable catheter having a tubular structure formed of a flexible material with physical properties of molecular orientation thus promoting longitudinal tearing along the length of the tubular structure. More specifically, Teflon is a preferred material because it can be longitudinally oriented through extrusion.
Finally, the Kling et al U.S. Pat. No. 4,412,832 shows a catheter tube of a semi-rigid material which is beveled at the distal end and scored longitudinally in one or more places to provide lines along which the catheter tube may be split or peeled apart.
Therefore, it is of concern with respect to the prior devices as to the process used and physical nature of the weakened area. That is to say that, the two main problems are the ease of manufacture without additional operating steps and the accuracy of producing the thinned area as a consequence of the forming process. Weakness beyond that required for splitting can cause failure during insertion particularly in the area of the tip of the catheter where the material is thinned to help insertion.
It is the object of this invention to show an extremely high strength material which allows requisite circumferential stress resistance even though areas of weakness extend from the tip of the catheter longitudinally up the catheter body.
It is still further an object of the present placement catheter of the splittable type to show a stripe composition and shape which defines the cross-sectional configuration of the area for the longitudinal line of weakness.
It is an object to teach a way in which a relatively sharp V-shaped line of weakness can be generated longitudinally along the body of the thin-walled polyurethane catheter having high circumferential or hoop strength transverse to the V-shaped groove but having relatively low shear tear strength along the line of the sharp inward point or bottom of the line of weakness. Consistent with the foregoing objects and in order to overcome the problems besetting the prior patent art, the disclosure herein teaches the preferred process method and resulting structure.